| From: | Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com> |
|---|---|
| To: | Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Rafia Sabih <rafia(dot)sabih(at)enterprisedb(dot)com>, Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>, Rajkumar Raghuwanshi <rajkumar(dot)raghuwanshi(at)enterprisedb(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Partition-wise join for join between (declaratively) partitioned tables |
| Date: | 2017-08-10 03:58:40 |
| Message-ID: | CAEepm=0VCrC-WfzZkq3YSvJXf225rDnp1ypjv+rjKO5d0=XqFg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Aug 10, 2017 at 1:39 AM, Thomas Munro
<thomas(dot)munro(at)enterprisedb(dot)com> wrote:
> On my computer it took ~1.5 seconds to plan a 1000 partition join,
> ~7.1 seconds to plan a 2000 partition join, and ~50 seconds to plan a
> 4000 partition join. I poked around in a profiler a bit and saw that
> for the 2000 partition case I spent almost half the time in
> create_plan->...->prepare_sort_from_pathkeys->find_ec_member_for_tle,
> and about half of that was in bms_is_subset. The other half the time
> was in query_planner->make_one_rel which spent 2/3 of its time in
> set_rel_size->add_child_rel_equivalences->bms_overlap and the other
> 1/3 in standard_join_search.
Ashutosh asked me how I did that. Please see attached. I was
explaining simple joins like SELECT * FROM foofoo JOIN barbar USING
(a, b). Here also is the experimental hack I tried when I saw
bitmapset.c eating my CPU.
--
Thomas Munro
http://www.enterprisedb.com
| Attachment | Content-Type | Size |
|---|---|---|
| bitmapset-track-leading-empty-space.patch | application/octet-stream | 4.3 KB |
| make-partitions.sh | application/x-sh | 2.0 KB |
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